Merry Naxxramas

Blizzard announces first wing of the Curse of Naxxramas expansion for
Hearthstone is now available, noting this is free for a limited time.
Here's how this works:

The first wing of Curse of Naxxramas™: A
Hearthstone™ Adventure has opened! Players can now put their decks to the test
against the malevolent undead who roam Azeroth’s most infamous floating
necropolis—without spending a single coin. The Arachnid Quarter, the first of
the Adventure’s five sinister wings, is now available—free for a limited time—to
all Hearthstone: Heroes of Warcraft™ players who step into the necropolis during
the Curse of Naxxramas launch event, taking place now through early September.

“Curse of Naxxramas introduces a whole new way to play Hearthstone”

Curse of Naxxramas pits solo Hearthstone players against a series of iconic,
necrotic bosses, each with its own unique powers and cards to command. Heroes
will need to draw on all of their wits and deck-building prowess to prevail over
Naxxramas’s horrors, earning a total of 30 new cards along the way that can be
used in regular play—including a new Legendary card for completing each wing.

“Curse of Naxxramas introduces a whole new way to play Hearthstone,” said Mike
Morhaime, CEO and cofounder of Blizzard Entertainment. “Players of all skill
levels will find plenty to challenge them within Naxxramas’s haunted
corridors—and plenty of new options for their decks with the new cards we’re
adding.”

A new wing of Naxxramas will open each week, and access to these four additional
wings may be purchased for 700 gold per wing or $6.99 per wing. Players can earn
the in-game gold needed to unlock the next wing by completing various quests or
emerging victorious from the game’s Arena mode—or they can choose to unlock the
next available Naxxramas wing using real money.